The present invention relates to an optical disc made of two laminated substrates, and which is generally referred to as an optical video disc or digital audio disc.
A cross section of a conventional optical disc is shown in FIG. 1 wherein a synthetic resin (e.g. acrylic resin) substrate 1 with information pits 1a formed on one side thereof is covered with a metallic (e.g. aluminum) reflecting film 2. The film 2 is further protected with an adhesive layer 3, and the substrate is laminated in face-to-face relation with another substrate 1' also having information pits 1a', a metallic reflecting film 2' and a protective adhesive layer 3'. Usually, the two substrates are bonded together with an epoxy or solvent type adhesive. However, epoxy adhesive cures slowly at ordinary temperatures, and furthermore, it entraps air and may have adverse effects on the vacuum-deposited metallic reflecting layer. On the other hand, the solvent type adhesive quite easily attacks the substrate if it is made of an acrylic resin.